Project Summary The retina, like many other regions of the nervous system, is subject to a variety of inherited and acquired degenerative conditions. These conditions often result in the degeneration of the photoreceptors, the main light sensing cells in the retina. Despite the loss of photoreceptors, the inner retinal circuitry is intact for many years, and this has led to the possibility of photoreceptor replacement as a potential therapy. Cell replacement strategy is important as the loss of photoreceptors in the mammalian retina is not associated with any effective regeneration from resident cells. A potential source of cellular replacement could be pluripotent stem cells. There are a number of groups looking into the potential of stem cell derived RPE including an approved clinical trial for RPE cell replacement for AMD and Stargardt dystrophy. However, as the disease progresses to vision loss, patients will require replacement of the lost photoreceptors cells as well. Although a number of groups have shown integration of photoreceptors in the mouse retina, the overall efficiency is really low. Additionally, the role of the microglia in this process has largely been unexplored. This proposal aims to look at the role of microglia-derived neurotrophic factors in both retinal repair and regenerative medicine. We will use a cross- species approach to identify and carry out basic studies in flies and apply the result in mammalian retinas.